Large grid connected synchronous generators are required to be protected from several
abnormal operating conditions that are both major and minor in nature. The generating units as such
require multiple protection devices to provide comprehensive protection against these fault conditions.
Amongst these protection functions, the Anti-motoring (ANSI Code-32) and Abnormal Frequency (ANSI
Code-81) protections are discussed in this paper. The concepts and possible control strategy for
implementation of these protection functions as a part of integrated multifunction generator protection
relay have been outlined and modelled using Matlab Simulink software. The power system used for
simulation was modelled using a separately excited large synchronous generating system connected to a
132 KV, 50 HZ transmission network through a high voltage breaker. The operation and performance of
both of the protection functions have been analysed by simulating time varying output of prime mover and
variable loads on the power system.